A PROSPECTIVE-STUDY OF PATIENTS WITH LUNG-CANCER AND HYPONATREMIA OF MALIGNANCY

This study was undertaken to define the impact of arginine vasopressin (AVP) and atrial natriuretic peptide (ANP) on sodium homeostasis in p atients with lung cancer. Patients had their serum and urine electroly tes and osmolality determined before and after a saline infusion of 50 0 ml. The plasma hormones, AVP, ANP, plasma renin activity (PRA), angi otensin II, and aldosterone were determined by radioimmunoassay every 15 min before, during and after the saline infusion. Fifty patients, 3 1 with small cell lung cancer and 19 with non-small cell lung cancer p articipated in this trial. All 11 patients (10 patients with small cel l lung cancer and one patient with non-small cell lung cancer) who pre sented with hyponatremia had inappropriately elevated levels of AVP. E levated plasma AVP levels were highly correlated with the presence of hyponatremia (p < 0.00001). Initial plasma ANP levels were not associa ted with hyponatremia (p = 0.73). Urinary sodium concentration increas ed during the saline infusion proportional to the initial plasma level of ANP (p = 0.0045). AVP appears to be elevated in nearly all patient s with hyponatremia of malignancy. ANP plasma levels in patients with lung cancer are associated with the ability to excrete a sodium load b ut do not appear to downregulate renin, angiotensin II, and aldosteron e production.